Temporal And Spatial Variation Characteristics Of Aerosol Optical Properties In Henan Province And Their Influencing Factors

Based on the aerosol product of MODIS/Terra C6.1 from 2001 to 2018 in Henan province,the temporal variation and spatial distribution characteristics of aerosol optical depth(AOD),the Angstrom wavelength index column(AE),aerosol column mass concentration(AMC)and fine mode fraction(FMF)were analyzed.The impact of meteorological factor on AOD was analyzed based on the meteorological data,MODIS products of normalized difference vegetation index(NDVI)and land surface temperature(LST),as well as social and economic statistical data.The multiple regression equation of aerosol optical thickness is established.The main conclusions were as follows:(1)The spatial distribution of AOD in all seasons was high in the east and low in the west,high in the north and low in the south.The spatial distribution of Angstrom wavelength index was opposite to that of AOD.AOD in spring and summer was significantly higher than that in autumn and winter.The AE value was the highest in summer and the lowest in spring,indicating that fine mode aerosols were the main aerosols in summer.AOD in the east and south of Henan Province showed an increasing trend from 2001 to 2010.AOD of Henan Province showed a downward trend from 2011 to 2018.In general,AOD in Henan Province showed a decreasing trend year by year from 2001 to 2018,and the monthly average value of AOD was the highest in June to July.The annual average value of AE index in Henan Province increased rapidly from2001 to 2010,and showed a decreasing trend after 2011,and the average monthly peak and valley value of AE index all decreased.(2)The mass concentration distribution of aerosol column in Henan Province was similar to the optical depth distribution,while the spatial distribution of fine particle proportion was basically opposite to the optical depth distribution.Due to the influence of dust aerosol,the average value of AMC was the largest and the FMF was the smallest in spring in Henan province.AMC in summer was slightly higher than that in autumn and winter,but FMF in summer was much higher than that in other seasons.the average annual AMC in most areas of Henan Province showed a decreasing trend from 2001 to 2018,while the average annual FMF showed an increasing trend.In particular,the average annual FMF in Henan Province from2012 to 2017 was higher than 0.5.In terms of monthly variation,the monthly mean value of AMC was the highest from April to May,and the monthly mean value of FMF was the highest from July to August.The average monthly peak-valley difference of AMC and FMF in Henan Province decreased after 2011,and the average monthly peak value of AMC showed a decreasing trend.(3)AOD was positively correlated with annual average temperature and relative humidity in the west and southwest of Henan Province,while AOD was negatively correlated with wind speed in the whole province.The correlation between wind speed and AOD was positive in spring and negative in other seasons.The correlation between precipitation and AOD was negative in spring.According to principal component analysis,the main influencing factors of aerosol optical thickness include population density,surface temperature and precipitation.